Direction-finder's range (7)
I believe the answer is:
compass
I believe this is a double definition.
'direction-finder's' is the first definition.
'range' is the second definition.
(compass can mean range or scope)
(Other definitions for compass that I've seen before include "Box the ---, change fully round" , "Instrument for determining direction from magnetic needle" , "Course guide" , "Direction finder; scope" , "Range - vessel's navigating instrument" .)